Motorcraft SP-514 spark plugs
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From: Carnegie, PA
Yeah, I knew the thread was initiated a lot longer than a year ago, I knew that there was some activity last year too, I know too that my '07 FX4 5.4-3v takes different plug numbers than the 4.6-3v in our '08 GT, but the plugs look to be made the same and have gone through similar updates. Thought a look at the changes would maybe help someone. I know the Lisle tools work for either as well. If a plug breaks, follow the Lisle Tool directions, it's engineered to do exactly the job.
Yes, my new plugs in the 5.4-3v got a thin smearing of nickel anti seize on the barrels & threads.
Yes, my new plugs in the 5.4-3v got a thin smearing of nickel anti seize on the barrels & threads.
Last edited by m05fastbackGT; Sep 8, 2020 at 10:33 PM.
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From: the beautiful "Shenandoah Valley of Virginia"
The 5.4L 3 valves do indeed take different part numbers than the 4.6L 3 valves. The 2005-early 2008 Mustang 3 valves take SP-547 plugs which are the latest revised design from Ford/Motorcraft where as the latest revision for the 5.4L 3 valves are SP-546. Although they may appear to be made the same? there's obviously a reason behind the plugs having different part numbers
My post wasn't intended to suggest SP546s be used in a 4.6-3v, rather it was intended to show differences in revisions through time. I'll venture to say that the same changes in manufacture steps / methods in revisions are essentially the same between the SP546s & SP547s. How the barrel below the threads is attached to the threaded body and the method of attachment or "forming of" the ground strap look to be the same change.
Example, I used SP546s in my 5.4-3v in my '07 FX4, and I'll leave the older SP515s in a box, and I'll use SP547s in the 4.6-3v in the '08 GT. The 8 still new SP515s I have left will fit in the '08 GT, but they are the wrong heat range.
Last edited by tbear853; Sep 9, 2020 at 06:40 PM.
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SUPERCHARGED RED ROCKET ------------------Master-Moderator
Joined: May 11, 2006
Posts: 10,648
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From: Carnegie, PA
The heat range differs slightly. That's governed by the distance from insulator end back to where it contacts the plug body, up inside the barrel. The longer that distance is, the hotter the plug tip stays in use.
My post wasn't intended to suggest SP546s be used in a 4.6-3v, rather it was intended to show differences in revisions through time. I'll venture to say that the same changes in manufacture steps / methods in revisions are essentially the same between the SP546s & SP547s. How the barrel below the threads is attached to the threaded body and the method of attachment or "forming of" the ground strap look to be the same change.
Example, I used SP546s in my 5.4-3v in my '07 FX4, and I'll leave the older SP515s in a box, and I'll use SP547s in the 4.6-3v in the '08 GT. The 8 still new SP515s I have left will fit in the '08 GT, but they are the wrong heat range.
My post wasn't intended to suggest SP546s be used in a 4.6-3v, rather it was intended to show differences in revisions through time. I'll venture to say that the same changes in manufacture steps / methods in revisions are essentially the same between the SP546s & SP547s. How the barrel below the threads is attached to the threaded body and the method of attachment or "forming of" the ground strap look to be the same change.
Example, I used SP546s in my 5.4-3v in my '07 FX4, and I'll leave the older SP515s in a box, and I'll use SP547s in the 4.6-3v in the '08 GT. The 8 still new SP515s I have left will fit in the '08 GT, but they are the wrong heat range.
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